Bis-urea gelators for curable ink applications

ABSTRACT

The disclosure provides curable inks including a bis-urea gelator having the structure of Formula I. 
     
       
         
         
             
             
         
       
     
     wherein R and R′ each, independently of the other, is a saturated aliphatic hydrocarbon group selected from the group consisting of (1) linear aliphatic groups, (2) branched aliphatic groups, (3) cyclic aliphatic groups, (4) aliphatic groups containing both cyclic and acyclic portions, any carbon atom of the saturated aliphatic hydrocarbon group may be optionally substituted with an alkyl group (cyclic or acyclic), wherein (1) and (2) groups have a carbon number of from about 1 to about 22 carbons, and wherein (3) and (4) groups have a carbon number of from about 4 to about 10 carbons; and X is selected from the group consisting of: (i) an alkylene group, (ii) an arylene group, (iii) an arylalkylene group, and (iv) an alkylarylene group.

CROSS REFERENCE TO RELATED APPLICATIONS

Reference is made to commonly owned and co-pending, U.S. patentapplication Ser. No. ______ (not yet assigned) entitled “UltravioletCurable Inks Comprising Bis-Urea Gelators” to Chopra et al. (AttorneyDocket No. 20120759-417883) filed electronically on the same day as thepresent application, the entire disclosures of which is incorporatedherein by reference in its entirety.

BACKGROUND

The present embodiments are directed to curable inks, such as e-beamcurable inks and ultraviolet (UV) curable inks. Curable inks generallyinclude at least one curable monomer, a colorant, and a radiationactivated initiator that initiates polymerization of curable componentsof the ink. In particular, the curable ink is an UV curable gel ink.More specifically, the curable ink is an UV curable ink including agelator. These UV curable gel ink compositions can be used for ink jetprinting in a variety of applications.

UV curable gel inks are known. They are for example disclosed in, forexample, U.S. Pat. Nos. 7,153,349, 7,259,275, 7,270,408, 7,271,284,7,276,614, 7,279,506, 7,279,587, 7,293,868, 7,317,122, 7,323,498,7,384,463, 7,449,515, 7,459,014, 7,531,582, 7,538,145, 7,541,406,7,553,011, 7,556,844, 7,559,639, 7,563,489, 7,578,587, 7,625,956,7,632,546, 7,674,842, 7,681,966, 7,683,102, 7,690,782, 7,691,920,7,699,922, 7,714,040, 7,754,779, 7,812,064, and 7,820,731, thedisclosures of each of which are totally incorporated herein byreference. UV curable gel inks can exhibit desirable characteristicssuch as improved hardness and scratch-resistance and improved adhesionto various substrates. Curable gel inks can also exhibit advantages inthat dot spread of the ink can be controlled, the ink does not bleedexcessively into the substrate, including porous substrates.

A key component of the curable gel inks is a phase-change gelling agent(or gelator) enabling wide substrate latitude, excellent adhesion, andenhanced pigment dispersion stability. There remains a need to exploreand identify new gelator molecules that are suitable for use asphase-change materials for curable inks, as thickeners for coatingformations, or in other printing applications, such as 3D printing. Thesharp increase in ink viscosity upon printing offers numerous advantagesover non-phase change inks, namely: controlled spread (dot gain) andminimum bleed-through (jet-through) on porous substrates, wide substratelatitudes, minimal paper cockle and distortion, and the ability torapidly build up raised print features for 3D printing withoutintermediate curing steps.

SUMMARY

According to embodiments illustrated herein, there is provided abis-urea gelator having a structure of Formula I:

wherein R and R′ each, independently of the other, is saturatedaliphatic hydrocarbon group selected from the group consisting of (1)linear aliphatic groups, (2) branched aliphatic groups, (3) cyclicaliphatic groups, (4) aliphatic groups containing both cyclic andacyclic portions, any carbon atom of the saturated aliphatic hydrocarbongroup may be optionally substituted with an alkyl group (cyclic oracyclic), wherein (1) and (2) groups have a carbon number of from about1 to about 22 carbons, and wherein (3) and (4) groups have a carbonnumber of from about 4 to about 10 carbons; and X is selected from thegroup consisting of: (i) an alkylene group, (ii) an arylene group, (iii)an arylalkylene group, and (iv) an alkylarylene group.

In further embodiments, there is provided a bis-urea gelator having astructure of Formula II:

wherein each R₂, each R₂′, each R₃, and each R₃′, independently of oneanother, is H or C₁-C₃ alkyl; each R₄, each R₄′, each R₅, and each R₅′,independently of one another, is H or methyl; n and n′ each,independently of the other, is from about 5 to from about 17; p is fromabout 1 to about 10; and Z and Z′ each, independently of the other, isselected from the group consisting of cyclopropylene, 1,2-cyclobutylene,1,3-cyclobutylene, cyclopentylene, 1,3-cyclopenylene, cyclohexylene,1,3-cyclohexylene, and 1,4-cyclohexylene.

In other embodiments, there is provided an apparatus for 3-D printingcomprising a bis-urea gelator having a structure of Formula I:

wherein R and R′ each, independently of the other, saturated aliphatichydrocarbon group selected from the group consisting of (1) linearaliphatic groups, (2) branched aliphatic groups, (3) cyclic aliphaticgroups, (4) aliphatic groups containing both cyclic and acyclicportions, any carbon atom of the saturated aliphatic hydrocarbon groupmay be optionally substituted with an alkyl group (cyclic or acyclic),wherein (1) and (2) groups have a carbon number of from about 1 to about22 carbons, and wherein (3) and (4) groups have a carbon number of fromabout 4 to about 10 carbons; and X is selected from the group consistingof: (i) an alkylene group, (ii) an arylene group, (iii) an arylalkylenegroup, and (iv) an alkylarylene group.

BRIEF DESCRIPTION OF THE DRAWINGS

The figure illustrates generally, by way of example, but not by way oflimitation, various embodiments discussed in the present document.

FIG. 1 illustrates the relationship between viscosity vs. temperaturefor an UV curable ink according to embodiments herein.

DETAILED DESCRIPTION

In the following description, it is understood that other embodimentsmay be utilized and structural and operational changes may be madewithout departure from the scope of the present embodiments disclosedherein.

In this specification and the claims that follow, singular forms such as“a,” “an,” and “the” include plural forms unless the content clearlydictates otherwise. All ranges disclosed herein include, unlessspecifically indicated, all endpoints and intermediate values. Inaddition, reference may be made to a number of terms that shall bedefined as follows:

The present embodiments are directed generally to bis-urea gelators.More specifically, disclosed herein are bis-urea gelators for use in UVcurable ink applications. In certain embodiments, the bis-urea gelatorscan be used in thickeners for coating formulations. In certainembodiments, the bis-urea gelators can be used in 3D printing. The sharpincrease in ink viscosity upon printing offers numerous advantages overnon-phase change inks, namely: controlled spread (dot gain) and minimumbleed-through (jet-through) on porous substrates, wide substratelatitudes, minimal paper cockle and distortion, and the ability torapidly build up raised print features for 3D printing withoutintermediate curing steps.

The present embodiments provide a bis-urea gelator having the structureof Formula I:

wherein R₁ and R₁′ each, independently of the other, can be a saturatedaliphatic hydrocarbon group selected from the group consisting of (1)linear aliphatic groups, (2) branched aliphatic groups, and (3) cyclicaliphatic groups, (4) aliphatic groups containing both cyclic andacyclic portions, wherein any carbon atom of the saturated aliphatichydrocarbon group may be optionally substituted with an alkyl group(cyclic or acyclic), and wherein (1) and (2) groups have a carbon numberof from about 1 to about 22 carbons, from about 8 to about 20 carbonatoms, from about 10 to about 20 carbon atoms, or from about 14 to about18 carbon atoms, and wherein (3) and (4) groups have a carbon number offrom about 4 to about 10 carbons, or from about 4 to about 8 carbons orfrom about 4 to about 6 carbons;X is selected from the group consisting of: (i) an alkylene group(wherein an alkylene group is a divalent aliphatic group or alkyl group,including linear and branched, cyclic and acyclic, and substituted andunsubstituted alkylene groups, and wherein heteroatoms, such as oxygen,nitrogen, sulfur, and the like may or may not be present in the alkylenegroup having from about 2 carbon atom to about 24 carbon atoms, such asfrom about 4 carbon atom to about 20 carbon atoms, or from about 6carbon atom to about 16 carbon atoms, (ii) an arylene group (wherein anarylene group is a divalent aryl group, including substituted andunsubstituted arylene groups) having from about 6 carbon atom to about16 carbon atoms, such as from about 6 carbon atoms to about 12 carbonatoms or from about 6 carbon atoms to about 8 carbon atoms, (iii) anarylalkylene group (wherein an arylalkylene group is a divalentarylalkyl group, including substituted and unsubstituted arylalkylenegroups, wherein the alkyl portion of the arylalkylene group can belinear or branched, and cyclic or acyclic, and wherein heteroatoms, suchas oxygen, nitrogen, sulfur, and the like may or may not be present inthe alkyl portion of the arylalkylene group) having from about 6 carbonatoms to about 32 carbon atoms, such as from about 6 carbon atoms toabout 22 carbon atoms, or from about 6 carbon atoms to about 12 carbonatoms, and (iv) an alkylarylene group (wherein an alkylarylene group isa divalent alkylaryl group, including substituted and unsubstitutedalkylarylene groups, wherein the alkyl portion of the alkylarylene groupcan be linear or branched, saturated or unsaturated, and cyclic oracyclic, and wherein heteroatoms, such as oxygen, nitrogen, sulfur, andthe like may or may not be present in the alkyl portion of thealkylarylene group) having from about 6 carbon atoms to about 32 carbonatoms, such as from about 6 carbon atoms to about 22 carbon atoms, orfrom about 6 carbon atoms to about 12 carbon atoms, wherein thesubstituents on the substituted alkylene, arylalkylene, and alkylarylenegroups can be an alkyl group, halogen, cyano, and mixtures thereof, andthe like, wherein two or more substituents can be joined together toform a ring. Unlimited examples of suitable substituents for X groupinclude:

In certain embodiments, the disclosure provides a bis-urea gelator ofFormula I wherein each one of R₁ and R₁′ is an unsubstituted linearaliphatic group. In other embodiments, each one of R₁ and R₁′ is alinear aliphatic group substituted with one or more C₁-C₃ alkyl, suchas, methyl, ethyl, propyl, etc.

In one embodiment, R₁ and R₁′ are the same as each other; in anotherembodiment, R₁ and R₁′ are different from each other.

In one embodiment, R₁ and R₁′ are the same as each other.

In certain embodiments, X is an alkylene group selected from the groupconsisting of (1) linear aliphatic groups, (2) branched aliphaticgroups, (3) cyclic aliphatic groups, (4) aliphatic groups containingboth cyclic and acyclic portions, any carbon atom of the saturatedaliphatic hydrocarbon group may be optionally substituted with an alkylgroup (cyclic or acyclic).

In certain embodiments, X is an an alkylene group, for instance,methylene, ethylene, propylene, tetramethylene, pentamethylene,hexamethylene, heptamethylene, octamethylene, butylene group, 2-methylpropylene group, 2-methyl tetramethylene group, 2,2-dimethyltrimethylene group, 2-ethyl trimethylene group, 2-methyl pentamethylenegroup, 3-methyl pentamethylene group, heptamethylene group, hepylenegroup, octamethylene group, 2-ethyl hexylene group, nonamethylene group,decamethylene group, and the like, cyclopropylene, 1,2-cyclobutylene,1,3-cyclobutylene, cyclopentylene, 1,3-cyclopenylene, cyclohexylene,1,3-cyclohexylene, 1,4-cyclohexylene, or the like, any carbon atoms ofthe alkylene group may be substituted or unsubstituted.

In certain embodiments, X is an aliphatic group containing both cyclicand acyclic portions. In one embodiment, the aliphatic group includesone cyclic portion. In another embodiment, the aliphatic group includesone or more cyclic portions. In certain embodiments, the one or morecyclic portions may be the same or different from one another. Infurther embodiments, the one or more cyclic portions are separated by anacyclic portion. In further embodiments, each one of the one or morecyclic portions is independently selected from cyclopropylene,1,2-cyclobutylene, 1,3-cyclobutylene, cyclopentylene, 1,3-cyclopenylene,cyclohexylene, 1,3-cyclohexylene, and 1,4-cyclohexylene. In certainembodiments, the acyclic portion includes a C₁-C₈ alkylene such asmethylene, ethylene, propylene, butylene, pentylene, hexylene, hepylene,or octylene. In certain embodiments, both the acyclic portion and thecyclic portion are unsubstituted. In other embodiments, one or both ofthe acyclic portion and the cyclic portion are substituted. In certainembodiments, the one or both of the acyclic portion and the cyclicportion are substituted with one or more C₁-C₃ alkyl, such as, methyl,ethyl, propyl, and the like.

In certain embodiments, the present disclosure provides a bis-ureagelator having the structure of Formula II:

wherein each R₂, each R₂′, each R₃, and each R₃′, independently of oneanother, is H or C₁-C₃ alkyl, such as, methyl, ethyl, propyl, etc.; eachR₄, each R₄′, each R₅, and each R₅′, independently of one another, is Hor methyl; n and n′ each, independently of the other, is from about 5 tofrom about 17, or from about 10 to from about 15; p is from about 1 toabout 10, from about 1 to about 6, or from about 1 to about 4; and Z andZ′ each, independently of the other, is selected from the groupconsisting of cyclopropylene, 1,2-cyclobutylene, 1,3-cyclobutylene,cyclopentylene, 1,3-cyclopenylene, cyclohexylene, 1,3-cyclohexylene, and1,4-cyclohexylene; wherein at least one of Z and Z′ is not null. Incertain embodiments, each one of R₂, R₂′, R₃, and R₃′ are H. In certainembodiments, R₄ and R₅ are methyl. In certain embodiments, R₄′ and R₅′are methyl.

In certain embodiments, the present disclosure provides a bis-ureagelator having the structure of Formula III:

wherein each R₄, each R₄′, each R₅, and each R₅′, independently of oneanother, is H or methyl; p is from about 1 to about 10, from about 1 toabout 6, or from about 1 to about 4. In certain embodiments, R₄ and R₅are methyl. In certain embodiments, R₄′ and R₅′ are methyl. In certainembodiments, R₄ and R₅ are H. In certain embodiments, R₄′ and R₅′ are H.

The bis-urea gelator of the present disclosure can be synthesized byreacting an isocyanate with a saturated aliphatic amine (i.e., R—NH₂,R′—NH₂). In general, one molar equivalent of isocyanate and two molarequivalents of linear aliphatic amine are used. A variety of isocyanatesmay be used in the synthesis such as, for example, hexamethylenediisocyanate (HDI), 4,4′-methylene dicyclohexyl diisocyanate (H12MDI),isophorone diisocyanate (IPDI), 1,12-diisocyanatododecane. Examples ofsaturated aliphatic amine include, but are not limited to stearylamine,isostearylamine, dodecylamine, and decylamine. Mixtures of linearaliphatic amines may be used in the synthesis. For example, a mixture oftwo saturated aliphatic amines may be used in the synthesis. When amixture of two saturated aliphatic amines is used, the molar ratio ofthe saturated aliphatic amines may be at about 50:50.

Many embodiments of the compounds thus prepared can exhibit gel-likebehavior in that they undergo a relatively sharp increase in viscosityover a relatively narrow temperature range when dissolved in a liquidcarrier such as those compounds that behave as curable monomers whenexposed to radiation such as ultraviolet light. One example of such aliquid carrier is a propoxylated neopentyl glycol diacrylate such asSR9003, commercially available from Sartomer Co. Inc. Another example ofsuch a liquid carrier is 1,6-hexanedioldiacrylate, namely SR238, akaHDDA, commercially available from Sartomer Co. Inc.

In some embodiments, the temperature at which the ink forms the gelstate is any temperature below the jetting temperature of the ink, inone embodiment any temperature that is about 5° C. or more below thejetting temperature of the ink. In one embodiment, the gel state can beformed at a temperature of at least about 25° C., at least about 30° C.,or no more than about 100° C., no more than about 70° C., or no morethan about 50° C., although the temperature can be outside of theseranges. A rapid and large increase in ink viscosity occurs upon coolingfrom the jetting temperature, at which the ink is in a liquid state, tothe gel temperature, at which the ink is in the gel state. The viscosityincrease is in one specific embodiment at least a 10²⁵ fold increase inviscosity.

It has been found that optimum transfer efficiency from an intermediatetransfer surface to a final recording sheet and optimum print qualitycan be achieved if the viscosity of the ink image deposited on theintermediate transfer member is greatly increased after jetting the ink,so as to obtain a stable and transferable image that will not smear. Asuitable gelling agent for the ink will gel the monomers/oligomers inthe ink vehicle quickly and reversibly and will demonstrate a narrowphase change transition, for example within a temperature range of fromabout 30° C. to about 100° C., or from about 30° C. to about 70° C.,although the transition range can be outside of these temperatureranges. The gel state of the ink in one specific embodiment exhibits aminimum of 10^(2.5) centipoise, and in another specific embodiment 10³centipoise, increase in viscosity at transferring temperatures, e.g., inone specific embodiment from about 30 to about 70° C., compared to theviscosity at the jetting temperature. One specific embodiment isdirected to gelator containing inks that rapidly increase in viscositywithin from about 5° C. to about 10° C. below the jetting temperatureand ultimately reach a viscosity above 10⁴ times the jetting viscosity,and in another embodiment about 10⁵ times the jetting viscosity,although the viscosity can be outside of these ranges.

When the inks are in the gel state, the viscosity of the ink is, in oneembodiments, at least about 1,000 centipoise, at least about 10,000centipoise, or at least about 100,000 centipoise, although the viscositycan be outside of these ranges. Viscosity values in the gel state are inone embodiment at least about 10³ centipoise, at least about 10^(4.5)centipoise, no more than about 10⁹ centipoise, or no more than about10^(6.5) centipoise, although the gel state viscosity can be outside ofthese ranges. The gel phase viscosity can vary with the print process.

The gelator compositions disclosed herein can, in at least someembodiments, act as an organic gelator in an UV curable ink to theviscosity of the ink within a desired temperature range. In particular,a gelator can in some embodiments form a semi-solid gel in the inkvehicle at temperatures below the specific temperature at which the inkis jetted. Generally, a gelator composition has a viscosity of fromabout 10² cps to about 10⁶ cps at a temperature between 85° C. to 22°C., a viscosity of from about 10^(2.5) cps to about 10^(5.5) cps at atemperature between 75 to 30° C., or a viscosity of from about 10³ cpsto about 10⁵ cps at a temperature between 70° C. to 35° C., or aviscosity of from about 10² cps to about 10³ cps at a temperaturebetween 60° C. to 22° C.

Carrier Material

The ink composition includes a carrier material, or a mixture of two ormore carrier materials. Examples of carrier materials include UV curablemonomer, and UV curable oligomer. The curable materials are typicallyliquid at 25° C. The term “curable” describes, for example, a materialthat may be cured via polymerization, including for example free radicalroutes, and/or in which polymerization is photoinitiated though use of aradiation-sensitive photoinitiator. The term “UV curable” or“ultraviolet curable” refers to curing upon exposure to a ultraviolet(UV) light source, i.e., having a wavelength of 200-400 nm, andincluding in the presence or absence of initiators.

Curable Monomers and Oligomers

Suitable curable monomers include, but are not limited to, diacrylates,such as, propoxylated neopentyl diacrylate, e.g., SR9003, commerciallyavailable from Sartomer Co. Inc., 1,6-hexanedioldiacrylate, e.g., SR238,aka HDDA, commercially available from Sartomer; polyacrylates, such asdipentaerythritol pentaacrylate, e.g., SR399, commercially availablefrom Sartomer Co. Inc., trimethylol propane triacrylate, pentaerythritoltetraacrylate, pentaerythritol triacrylate, dipentaerythritolpentaacrylate, glycerol propoxy triacrylate, tris(2-hydroxyethyl)isocyanurate triacrylate, pentaacrylate ester; and the like; epoxyacrylates; urethane acrylates; amine acrylates; acrylic acrylates;acrylated esters; acrylated polyesters; acrylated ethers; acrylatedpolyethers; and the like. Mixtures of two or more materials can also beemployed as the reactive monomer. Suitable reactive monomers arecommercially available from, for example, Sartomer Co., Inc., BASFCorporation, Rahn AG., and the like. In embodiments, the at least oneradiation curable oligomer and/or monomer can be cationically curable,radically curable, or the like.

Specific examples of suitable acrylated oligomersinclude, but are notlimited to, acrylated polyester oligomers, such as CN2262 (SartomerCo.), EB 812 (Cytec Surface Specialties), EB 810 (Cytec SurfaceSpecialties), CN2200 (Sartomer Co.), CN2300 (Sartomer Co.), and thelike, acrylated urethane oligomers, such as EB270 (Cytec SurfaceSpecialties), EB 5129 (Cytec Surface Specialties), CN2920 (SartomerCo.), CN3211 (Sartomer Co.), and the like, and acrylated epoxyoligomers, such as EB 600 (Cytec Surface Specialties), EB 3411 (CytecSurface Specialties), CN2204 (Sartomer Co.), CN110 (Sartomer Co.), andthe like; and pentaerythritol tetraacrylate oligomers, such as SR399LV(Sartomer Co.) and the like.

The curable monomer or oligomer in embodiments is included in the ink inan amount of, for example, from about 20 to about 90 weight percent ofthe ink, such as from about 30 to about 85 weight percent, or from about40 to about 80 weight percent by weight of the total ink composition,although the amount can be outside of these ranges. In embodiments,mixtures of curable monomer optionally with oligomer are selected tohave a viscosity at 25° C. of about 1 to about 50 cP, such as about 1 toabout 40 cP or about 10 to about 30 cP, although the amount can beoutside of these ranges. In one embodiment, the mixture of curablemonomer and oligomer has a viscosity at 25° C. of about 20 cP. Also, insome embodiments, it is desired that the curable monomer or oligomer isnot a skin irritant, so that uncured ink compositions are not irritableto users.

Additives

The curable ink composition may also include one or more additives, suchas but are not limited to photoinitiator, colorant, wax, cross-linkingagent, additives, stabilizer and antioxidant.

Photoinitiator

The ink compositions further comprise a photoinitiator. Examples of freeradical photoinitiator include benzyl ketones, monomeric hydroxylketones, polymeric hydroxyl ketones, α-amino ketones, acyl phosphineoxides, metallocenes, benzophenone, benzophenone derivatives, and thelike. Specific examples include 1-hydroxy-cyclohexylphenylketone,benzophenone,2-benzyl-2-(dimethylamino)-1-(4-(4-morphorlinyl)phenyl)-1-butanone,2-methyl-1-(4-methylthio)phenyl-2-(4-morphorlinyl)-1-propanone,diphenyl-(2,4,6-trimethylbenzoyl) phosphine oxide, phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide, benzyl-dimethylketal,isopropylthioxanthone (DAROCUR ITX, available from BASF),2,4,6-trimethylbenzoyldiphenylphosphine oxide (available as BASF LUCIRINTPO), 2,4,6-trimethylbenzoylethoxyphenylphosphine oxide (available asBASF LUCIRIN TPO-L), bis(2,4,6-trimethylbenzoyl)-phenyl-phosphine oxide(available as BASF IRGACURE 819) and other acyl phosphines,2-methyl-1-(4-methylthio)phenyl-2-(4-morphorlinyl)-1-propanone(available as BASF IRGACURE 907) and1-(4-(2-hydroxyethoxy)phenyl)-2-hydroxy-2-methylpropan-1-one (availableas BASF IRGACURE 2959), 2-benzyl 2-dimethylamino 1-(4-morpholinophenyl)butanone-1 (available as BASF IRGACURE 369),2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)-benzyl)-phenyl)-2-methylpropan-1-one(available as BASF IRGACURE 127),2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-ylphenyl)-butanone(available as BASF IRGACURE 379), titanocenes, isopropylthioxanthone,1-hydroxy-cyclohexylphenylketone, 2,4,6-trimethylbenzophenone,4-methylbenzophenone, 2,4,6-trimethylbenzoylphenylphosphinic acid ethylester, oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl) propanone),2-hydroxy-2-methyl-1-phenyl-1-propanone, benzyl-dimethylketal,isopropyl-9H-thioxanthen-9-one, alpha amino ketone (IRGACURE 379),oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone](available as Esacure KIP 150 from Lamberti); and the like, as well asmixtures thereof.

Optionally, the curable inks can also contain an amine synergist, whichare co-initiators which can donate a hydrogen atom to a photoinitiatorand thereby form a radical species that initiates polymerization, andcan also consume dissolved oxygen, which inhibits free-radicalpolymerization, thereby increasing the speed of polymerization. Examplesof suitable amine synergists include (but are not limited to)ethyl-4-dimethylaminobenzoate, 2-ethylhexyl-4-dimethylaminobenzoate, andthe like, as well as mixtures thereof.

Initiators for inks disclosed herein can absorb radiation at any desiredor effective wavelength, in one embodiment at least about 200nanometers, and in one embodiment no more than about 560 nanometers, andin another embodiment no more than about 420 nanometers, although thewavelength can be outside of these ranges.

The initiator can be present in the ink in any desired or effectiveamount, in one embodiment at least about 0.5 percent by weight of thecarrier, and in another embodiment at least about 1 percent by weight ofthe carrier, and in one embodiment no more than about 15 percent byweight of the carrier, and in another embodiment no more than about 10percent by weight of the carrier, although the amount can be outside ofthese ranges.

Colorants

The UV curable ink according to the present disclosure may be producedas a colored ink by adding a colorant during ink production.Alternatively, an UV curable ink lacking a colorant may be printed on asubstrate during a first pass, followed by a second pass. For example,each UV curable ink can be stored in a separate reservoir. The printingsystem delivers each ink separately to the substrate, and the two inksinteract. The UV curable inks may be delivered to the substratesimultaneously or consecutively. Any desired or effective colorant canbe employed in the ink compositions, including pigment, dye, mixtures ofpigment and dye, mixtures of pigments, mixtures of dyes, and the like.

Any suitable colorant may be used in embodiments herein, including dyes,pigments, or combinations thereof. As colorants, examples may includeany dye or pigment capable of being dispersed or dissolved in thevehicle. Examples of suitable pigments include, for example, PaliogenViolet 5100 (BASF); Paliogen Violet 5890 (BASF); Heliogen Green L8730(BASF); Lithol Scarlet D3700 (BASF); SUNFAST® Blue 15:4 (Sun Chemical249-0592); HOSTAPERM Blue B2G-D (Clariant); Permanent Red P-F7RK;HOSTAPERM Violet BL (Clariant); Lithol Scarlet 4440 (BASF); Bon Red C(Dominion Color Company); Oracet Pink RF (Ciba); Paliogen Red 3871 K(BASF); SUNFAST® Blue 15:3 (Sun Chemical 249-1284); Paliogen Red 3340(BASF); SUNFAST® Carbazole Violet 23 (Sun Chemical 246-1670); LitholFast Scarlet L4300 (BASF); Sunbrite Yellow 17 (Sun Chemical 275-0023);Heliogen Blue L6900, L7020 (BASF); Sunbrite Yellow 74 (Sun Chemical272-0558); SPECTRA PAC® C Orange 16 (Sun Chemical 276-3016); HeliogenBlue K6902, K6910 (BASF); SUNFAST® Magenta 122 (Sun Chemical 228-0013);Heliogen Blue D6840, D7080 (BASF); Sudan Blue OS (BASF); Neopen BlueFF4012 (BASF); PV Fast Blue B2G01 (Clariant); Irgalite Blue BCA (Ciba);Paliogen Blue 6470 (BASF); Sudan Orange G (Aldrich); Sudan Orange 220(BASF); Paliogen Orange 3040 (BASF); Paliogen Yellow 152, 1560 (BASF);Lithol Fast Yellow 0991 K (BASF); Paliotol Yellow 1840 (BASF); NovopermYellow FGL (Clariant); Lumogen Yellow D0790 (BASF); Suco-Yellow L1250(BASF); Suco-Yellow D1355 (BASF); Suco Fast Yellow DI 355, DI 351(BASF); Hostaperm Pink E 02 (Clariant); Hansa Brilliant Yellow 5GX03(Clariant); Permanent Yellow GRL 02 (Clariant); Permanent Rubine L6B 05(Clariant); Fanal Pink D4830 (BASF); Cinquasia Magenta (Du Pont),Paliogen Black L0084 (BASF); Pigment Black K801 (BASF); and carbonblacks such as REGAL 33Q™ (Cabot), Carbon Black 5250, Carbon Black 5750(Columbia Chemical), mixtures thereof and the like. Examples of suitabledyes include Usharect Blue 86 (Direct Blue 86), available from UshantiColor; Intralite Turquoise 8GL (Direct Blue 86), available from ClassicDyestuffs; Chemictive Brilliant Red 7BH (Reactive Red 4), available fromChemiequip; Levafix Black EB, available from Bayer; Reactron Red H8B(Reactive Red 31), available from Atlas Dye-Chem; D&C Red #28 (Acid Red92), available from Warner-Jenkinson; Direct Brilliant Pink B, availablefrom Global Colors; Acid Tartrazine, available from MetrochemIndustries; Cartasol Yellow 6GF Clariant; Carta Blue 2GL, available fromClariant; and the like. Example solvent dyes include spirit soluble dyessuch as Neozapon Red 492 (BASF); Orasol Red G (Ciba); Direct BrilliantPink B (Global Colors); Aizen Spilon Red C-BH (Hodogaya Chemical);Kayanol Red 3BL (Nippon Kayaku); Spirit Fast Yellow 3G; Aizen SpilonYellow C-GNH (Hodogaya Chemical); Cartasol Brilliant Yellow 4GF(Clariant); Pergasol Yellow CGP (Ciba); Orasol Black RLP (Ciba); SavinylBlack RLS (Clariant); Morfast Black Conc. A (Rohm and Haas); Orasol BlueGN (Ciba); Savinyl Blue GLS (Sandoz); Luxol Fast Blue MBSN (Pylam);Sevron Blue 5GMF (C₁₋assic Dyestuffs); Basacid Blue 750 (BASF), NeozaponBlack X51 [C.I. Solvent Black, C.I. 12195] (BASF), Sudan Blue 670 [C.I.61554] (BASF), Sudan Yellow 146 [C.I. 12700] (BASF), Sudan Red 462 [C.I.260501] (BASF), mixtures thereof and the like.

The colorant is present in the curable ink in any desired or effectiveamount to obtain the desired color or hue, in embodiments from about 0.1percent to about 15 percent by weight of the ink, or from about 0.2percent to about 8 percent by weight of the ink, although the amount canbe outside of these ranges.

Wax

The curable ink further contains at least one wax. The wax can becurable or non-curable. The wax may be any wax component that ismiscible with the other ink components. Inclusion of the wax promotes anincrease in viscosity of the ink as it cools from the jettingtemperature.

Desirably, the wax composition is curable so as to participate in thecuring of the ink. Suitable examples of curable waxes include those thatare functionalized with curable groups. The curable groups may include,for example, acrylate, methacrylate, alkene, allylic ether, epoxideand/or oxetane groups. These waxes can be synthesized by the reaction ofa wax equipped with a transformable functional group, such as carboxylicacid, hydroxyl and the like. The functionalized wax is also able toparticipate in the ultraviolet light initiated cure and thus does notlower the final robustness of the image. Additionally, the wax acts as abinder, preventing syneresis, and in printing, acts as a barrier orcoating on paper/image receiving substrate, preventing the principlecarrier from wicking or showing through the paper. The curable wax alsoreduces haloing tendency.

In embodiments, the optional curable wax is included in the ink in anamount of from, for example, about 1 to about 25% by weight of the ink,such as from about 2 to about 20% by weight of the ink, or from about2.5 to about 15% by weight of the ink.

Antioxidant

The ink composition can also optionally contain an antioxidant. Theoptional antioxidants of the ink compositions protect the images fromoxidation and also protect the ink components from oxidation during theheating portion of the ink preparation process. Specific examples ofsuitable antioxidants include NAUGUARD® series of antioxidants such asNAUGUARD® 445, NAUGUARD® 524, NAUGUARD® 76, and NAUGUARD® 5112(commercially available from Chemtura Corporation, Philadelphia, Pa.),the IRGANOX® series of antioxidants such as IRGANOX® 10310 (commerciallyavailable from BASF), IRGASTAB® UV10 (commercially available from CibaSpecialty Chemicals), and the like. When present, the optionalantioxidant can be present in the ink in any desired or effectiveamount, such as in an amount of from at least about 0.01 to about 20percent by weight of the ink, such as about 0.1 to about 5 percent byweight of the ink, or from about 1 to about 3 percent by weight of theink, although the amount can be outside of these ranges.

Preparation of Ink

The ink composition of the present disclosure can be prepared by anydesired or suitable method. For example, in the case of curable gel UVinks the ink ingredients can be mixed together, followed by heating,typically to a temperature of from about 50° C. to about 100° C.,although the temperature can be outside of this range, and stirringuntil a homogeneous ink composition is obtained, followed by cooling theink to ambient temperature (typically from about 20° C. to about 25°C.). In the case of liquid ink compositions, the ink ingredients cansimply be mixed together with stirring to provide a homogeneouscomposition, although heating can also be used if desired or necessaryto help form the composition. Other methods for making ink compositionsare known in the art and will be apparent based on the presentdisclosure.

Printing of the Ink

The curable ink may generally be printed on a suitable substrate suchas, without limitation, paper, glass art paper, bond paper, paperboard,Kraft paper, cardboard, semi-synthetic paper or plastic sheets, such aspolyester or polyethylene sheets, and the like. These various substratescan be provided in their natural state, such as uncoated paper, or theycan be provided in modified forms, such as coated or treated papers orcardboard, printed papers or cardboard, and the like.

Specific suitable papers include plain papers such as XEROX 4200 papers,XEROX Image Series papers, ruled notebook paper, bond paper, silicacoated papers such as Sharp Company silica coated paper, JuJo paper,HAMMERMILL LASERPRINT paper, and the like, glossy coated papers such asXEROX Digital Color Gloss, Sappi Warren Papers LUSTROGLOSS, specialtypapers such as Xerox DURAPAPER, and the like.

Further suitable materials may be used, including but not limited to,transparency materials, fabrics, textile products, plastics, polymericfilms, inorganic recording mediums such as metals and wood, and thelike, transparency materials, fabrics, textile products, plastics,polymeric films, inorganic substrates such as metals and wood, and thelike.

The inks described herein are further illustrated in the followingexamples. All parts and percentages are by weight unless otherwiseindicated.

It will be appreciated that various of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be desirablycombined into many other different systems or applications. Also,various presently unforeseen or unanticipated alternatives,modifications, variations or improvements therein may be subsequentlymade by those skilled in the art, and are also intended to beencompassed by the following claims.

While the description above refers to particular embodiments, it will beunderstood that many modifications may be made without departing fromthe spirit thereof. The accompanying claims are intended to cover suchmodifications as would fall within the true scope and spirit ofembodiments herein.

The presently disclosed embodiments are, therefore, to be considered inall respects as illustrative and not restrictive, the scope ofembodiments being indicated by the appended claims rather than theforegoing description. All changes that come within the meaning of andrange of equivalency of the claims are intended to be embraced therein.

EXAMPLES

The examples set forth herein below and are illustrative of differentcompositions and conditions that can be used in practicing the presentembodiments. All proportions are by weight unless otherwise indicated.It will be apparent, however, that the present embodiments can bepracticed with many types of compositions and can have many differentuses in accordance with the disclosure above and as pointed outhereinafter.

Example 1 Synthesis of Bis-Urea Gelators

Into a solution containing Desmodur W (H12MDI, 4.91 g, 18.70 mmol;obtained from Bayer) and hexane (40 milliliters) with stirring at roomtemperature was added stearylamine (10.08 g, 37.4 mmol; obtained fromSigma-Aldrich Fine Chemicals). The resulting solution was heated toreflux for 1 hour. The IR spectrum indicated that all isocyanate wasconsumed. The solution was cooled to room temperature during which awhite fluffy precipitate was formed. The product was filtered on aBuchner funnel and the filtercake was washed with hexanes and dried on avacuum pump to furnish 15 g (18.7 mmol, 100% yield) of a white fluffysolid.

Compound 2 is prepared according to the same procedure as compound 1except that isostearylamine is used in place of stearylamine.

Example 2 Gelation Test

5 weight percent of Compound 1 was dissolved in acrylate monomer (SR003,propoxylated neopentyl glycol diacrylate; orSR238,1,6-hexanedioldiacrylate, aka HDDA) and heated to 90° C. for 30minutes. The mixture was cooled to room temperature and checked forgelation behavior. Compound 1 formed a gel in either SR9003 or HDDA,both are suitable ink vehicles for UV curable inks.

Example 3 Preparation of Cyan Pigment Dispersion

To a 4L jacketed stainless steel container was added SR9003 (1166.2 g)and EFKA (BASF dispersant, 993.8 g of a 32.4 solids in SR9003). This wasstirred using a high speed mixer and to this was added cyan pigment (SUNspectrapac, 540 g) over 1 hour. The mixer was replaced with a basketmill (Hockmeyer, 0.1 mm screan) containing Zirconium beads (0.3 mm, 40g) and the RPM was increased to 5500 over 5 minutes while cooling thejacketed reactor. Upon reaching 5500 rpm the basket mill was operatedfor 3 hours while maintaining a reaction temperature of 90° C. Thebasket mill was raised and the dispersion was discharged to afford acyan dispersion of 20% solids content.

Example 4 General Procedure for Ink Formation

To a 20 mL amber glass vial was added 1.0 g Compound 1, 0.4 g Unilin350-acrylate (reactive wax phase change agent, derived from UNILIN 350,which is available from Baker Petrolite), 14.1 SR9003 or SR238 monomer,1.0 g SR399LV, 0.6 g Irgacure 379 (an α-amino ketone photoinitiator,available from Ciba Specialty Chemicals, Inc.), 0.1 g Irgacure 819, 0.8g Esacure KIP150, 0.04 g and Irgastab UV10 (an ultra-violetphotoinitator, available from Ciba Specialty Chemicals, Inc.), and 20%Cyan pigment concentrate dispersion in SR9003. The mixture was stirredwith a magnetic stir bar and heated to 90° C. for 1 hour to form a clearsolution (the ink base). To the hot ink base was added a pigmentdispersion concentrate (15 wt % Cyan pigment in SR9003 monomer) and theresulting mixture was heated with stirring for an additional hour at 90°C.

It is understood that when selecting specific amounts for individual inkcomponents, the sum of all the components in the final ink adds to 100%.

TABLE 1 (Ink with Gelator 1) Component Weight % m/g Compound 1 5.00 1.0Unilin 350-acrylate 2.00 0.4 SR238 monomer 70.30 14.1 SR399LV 5.00 1.0Irgacure 379 3.00 0.6 Irgacure 819 0.50 0.1 Esacure KIP150 4.00 0.8Irgastab UV10 0.20 0.04 20 wt % Cyan pigment 10.00 2.0 dispersion inSR9003 TOTAL 100.0 20.0

Example 5 Rheology of Ink containing Bis-Urea Gelators

Temperature dependent complex viscosity of an ink containing thebis-urea gelator was measured. The data was measured using acontrolled-strain rheometer from TA Instruments (RFS-3) at a constantfrequency of 1 Hz. The bis-urea gelators can cover a wide scope ofviscosity ranges, and can be tuned for optimum phase change temperatureand ultimate viscosity at room temperature, which can be advantageousfor non-contact leveling of our inks, or for printing of 3D objects, forexample. Table 2 summarizes the viscosity data for the Cyan ink inExample 4.

TABLE 2 Temperature/Time Viscosity Data for Cyan Ink (Example 4 - Inkwith Gelator 1) Complex Tan Temp/° C. Viscosity/cps G′/Pa G″/Pa delta 902.41 0.001249 0.015098 12.08498 85 2.75 0.001048 0.017274 16.48775 802.97 0.001318 0.018631 14.14031 75 3.27 0.000937 0.020524 21.89315 704.38 0.001531 0.027483 17.95013 65 5.90 0.001716 0.037045 21.58704 609.11 0.003176 0.057153 17.99729 55 15.2 0.008206 0.09515 11.59553 5025.14 0.016647 0.157096 9.436766 45 45.53 0.038269 0.283479 7.407627 4087.49 0.089339 0.542418 6.071439 35 167.07 0.192829 1.031884 5.351281 30318.93 0.399234 1.963686 4.918634

All the patents and applications referred to herein are herebyspecifically, and totally incorporated herein by reference in theirentirety in the instant specification.

1. A bis-urea gelator having a structure of Formula I:

wherein R and R′ each having from 14 to 18 carbon atoms, independentlyof the other, is saturated aliphatic hydrocarbon group selected from thegroup consisting of (1) linear aliphatic groups, (2) branched aliphaticgroups, (3) cyclic aliphatic groups, (4) aliphatic groups containingboth cyclic and acyclic portions, any carbon atom of the saturatedaliphatic hydrocarbon group may be optionally substituted with an alkylgroup (cyclic or acyclic), wherein (1) and (2) groups have a carbonnumber of from 1 to 22 carbons, and wherein (3) and (4) groups have acarbon number of from 4 to 10 carbons; and X is an aliphatic groupcontaining both cyclic and acyclic portions, any carbon atom of thealiphatic hydrocarbon group may be optionally substituted with an alkylgroup (cyclic or acyclic).
 2. (canceled)
 3. (canceled)
 4. The gelatoraccording to claim 1, wherein each one of R₁ and R₁′ is an unsubstitutedlinear aliphatic group.
 5. The gelator according to claim 1, whereineach one of R₁ and R₁′ is a linear aliphatic group substituted with oneor more C₁-C₃ alkyl.
 6. The gelator according to claim 1, wherein R₁ andR₁′ are the same as each other.
 7. The gelator according to claim 1,wherein R₁ and R₁′ are different from each other.
 8. (canceled) 9.(canceled)
 10. The gelator according to claim 1, wherein the aliphaticgroup comprises one or more cyclic portions.
 11. The gelator accordingto claim 10, wherein each one of the one or more cyclic portions isindependently selected from the group consisting of cyclopropylene,1,2-cyclobutylene, 1,3-cyclobutylene, cyclopentylene, 1,3-cyclopenylene,cyclohexylene, 1,3-cyclohexylene, and 1,4-cyclohexylene.
 12. The gelatoraccording to claim 1, wherein the acyclic portion comprises a C₁-C₈alkylene.
 13. (canceled)
 14. A bis-urea gelator having a structure ofFormula II:

wherein each R₂, each R₂′, each R₃, and each R₃′, independently of oneanother, is H or C₁-C₃ alkyl; each R₄, each R₄′, each R₅, and each R₅′,independently of one another, is H or methyl; n and n′ each,independently of the other, is from 10 to 15; p is from 1 to 10; and Zand Z′ each, independently of the other, is selected from the groupconsisting of null, cyclopropylene, 1,2-cyclobutylene,1,3-cyclobutylene, cyclopentylene, 1,3-cyclopenylene, cyclohexylene,1,3-cyclohexylene, and 1,4-cyclohexylene, wherein at least one of Z andZ′ is not null.
 15. The gelator according to claim 14, wherein the Z andZ′ are each 1,4-cyclohexylene and p is from 1 to
 4. 16-20. (canceled)21. The gelator according to claim 11, wherein the each one of the oneor more cyclic portions is 1,4-cyclohexylene.
 22. The gelator accordingto claim 12, wherein the acyclic portion is methylene.
 23. The gelatoraccording to claim 14, wherein at least one of Z and Z′ is not null. 24.The gelator according to claim 14, wherein R₄, R₄′, R₅, and R₅′ aremethyl.
 25. A bis-urea gelator having a structure of Formula III:

wherein R₄, R₄′, R₅, and R₅′, independently of one another, is H ormethyl; and p is from about 1 to about
 10. 27. The gelator according toclaim 25, wherein R₄, R₄′, R₅, and R₅′ are methyl.
 28. The gelatoraccording to claim 27, p is 1.